Refractory metal silicide target, method of manufacturing the target, refractory metal silicide thin film, and semiconductor device

ABSTRACT

A refractory metal silicide target is characterized by comprising a fine mixed structure composed of MSi 2  (where M: refractory metal) grains and Si grains, wherein the number of MSi 2  grains independently existing in a cross section of 0.01 mm 2  of the mixed structure is not greater than 15, the MSi 2  grains have an average grain size not greater than 10 μm, whereas free Si grains existing in gaps of the MSi 2  grains have a maximum grain size not greater than 20 μm. The target has a high density, high purity fine mixed structure with a uniform composition and contains a small amount of impurities such as oxygen etc. The employment of the target can reduce particles produced in sputtering, the change of a film resistance in a wafer and the impurities in a film and improve yield and reliability when semiconductors are manufactured.

TECHNICAL FIELD

[0001] The present invention relates to a refractory metal silicidetarget, a method of manufacturing the target, a refractory metalsilicide thin film, and a semiconductor device, and more specifically,to a refractory metal silicide target, a method of simply manufacturingthe target, a refractory metal silicide thin film, and a semiconductordevice capable of reducing the generation of particles in sputtering andforming a thin film of high quality by densifying or fining a mixedstructure and making a uniform composition and further achieving highdensity and high purification.

BACKGROUND ART

[0002] A sputtering method is employed as one of the effective methodsof forming a refractory metal silicide thin film used for a gateelectrode, source electrode, drain electrode of semiconductor devicessuch as MOS, LSI devices and the like and for wiring. The sputteringmethod, which is excellent in mass-productivity and the stability of aformed film, is a method such that argon ions are caused to collide witha disc-shaped refractory metal silicide target and discharge a targetconstituting metal which is deposited as a thin film on a substratedisposed in confrontation with the target. Consequently, the property ofthe silicide thin film formed by sputtering greatly depends upon thecharacteristics of the target.

[0003] Recently, as a semiconductor device is highly integrated andminiaturized, it is required that a sputtering target used to form arefractory metal silicide thin film produces a less amount of particles(fine grains). That is, since particles produced from a target duringsputtering have a very fine grain size of about 0.1-10 μm, when theparticles are mixed into a thin film being deposited, they cause aserious problem that the yield of semiconductor devices is greatlyreduced by the occurrence of short circuit between wires of a circuitand insufficient opening of wires. Thus, the reduction of an amount ofparticles is strongly required.

[0004] Since it can become effective means to miniaturize a targetstructure, that is, to make the size of MSi₂ grains and free Si grainsas small as possible in order to reduce an amount of particles producedfrom a target, there are conventionally proposed various manufacturingmethods of miniaturizing the structure.

[0005] For example, Japanese Patent Application Laid-Open No. Sho63(1988)-219580 discloses that a high density target having a finestructure and containing a small amount of oxygen can be obtained insuch a manner that a mixed powder obtained by mixing a high purityrefractory metal powder with a high purity silicon powder is subjectedto a silicide reaction in high vacuum and a semi-sintered body isformed, then the resultant semi-sintered body is charged into apressure-tight sealing canister without being crushed and thepressure-tight sealing canister is sintered by a hot isostatic pressafter having evacuated and sealed. In this case, the thus obtainedtarget has a fine structure having the maximum grain size of MSi₂ notgreater than 20 μm and the maximum grain size of free Si not greaterthan 50 μm and containing oxygen not greater than 200 ppm with a densityratio not less than 99%.

[0006] Further, Japanese Patent Application Laid-Open No. Hei2(1990)-47261 discloses that a high density target with a fine structurecan be obtained in such a manner that a mixed powder of a high purityrefractory metal powder and a high purity silicon powder is subjected toa silicide reaction in high vacuum and a semi-sintered body is formed,then the semi-sintered body is crushed to not greater than 150 μm andfurther added and mixed with a high purity silicon powder and chargedinto a pressure-tight sealing canister, then the pressure-tight sealingcanister is sintered by a hot isostatic press after having evacuated andsealed. In this case, the thus obtained target has a maximum grain sizeof MSi₂ not greater than 20 μm and a density ratio not less than 99%with only free Si existing in a grain boundary.

[0007] Recently, as a semiconductor device is highly integrated andminiaturized, a high purity target containing a very small amount ofimpurities, which deteriorate the characteristics of the semiconductordevice, is required as a sputtering target used to form a refractorymetal silicide thin film. In particular, it is strongly required tominimize an amount of oxygen in a target because oxygen, whichconcentrates on the interface between a silicide layer and an underlayer and increases a film resistance, delays signals and lowers thereliability of the device.

[0008] Since it is effective oxygen reducing means to make deoxidationby heating a semi-sintered body as a material in vacuum and volatilizingoxygen in the form of silicon oxide (SiO or SiO₂), the followingmanufacturing methods of reducing oxygen are conventionally proposed.

[0009] For example, Japanese Patent Application Laid-Open No. Sho62(1987)-171911 obtains Mo silicide or W silicide each containing asmall amount of oxygen in such a manner that a mixed powder obtained bymixing a Mo powder or W powder with a Si powder is heated in vacuum at atemperature less than 800-1300° C. and a Mo silicide powder or Wsilicide powder is synthesized, then the resultant powder is held invacuum at 1300-1500° C. to remove oxygen as SiO by excessive Si.

[0010] On the other hand, a trial for optimizing the grain size of amaterial powder and hot pressing conditions from a view point that thecondensation of free Si results to an increase of particles produced andthe following manufacturing method is proposed.

[0011] For example, Japanese Patent Application Laid-Open No. Sho63(1988)-74967 obtains a target from which condensed silicon is removedin such a manner that a mixed powder obtained by adding a synthesizedsilicide powder of −100 mesh with a silicon powder of −42 mesh is heatedto 1300-1400° C. while applying a preload of 60-170 kg/cm², then pressedwith a pressing pressure of 200-400 kg/cm² and held after being pressed.

[0012] Further, Japanese Patent Application Laid-Open No. Sho64(1989)-39374 obtains a target from which condensed silicon is removedin such a manner that two types of synthesized silicide powders of −100mesh having a different composition are prepared and a mixed powderadjusted to have an intended composition is hot pressed under the sameconditions as above.

[0013] There is a problem, however, that when all the amounts of a mixedpowder necessary to form a single target is subjected to a silicidesynthesis at once in high vacuum in the above conventional manufacturingmethods, resulting MSi₂ grains are rapidly grown and coarsened as wellas cracks are made to an entire semi-sintered body by a rapidlyincreased temperature in a silicide reaction because the silicidereaction is an exothermic reaction, and when the semi-sintered body issintered by pressing in the state as it is, a resultant sintered bodycannot be used because the cracks remain.

[0014] There is also a problem that since a mixed material powderoverflows from a vessel by the rapid increase of temperature in thesilicide reaction and a composition is out of an intended compositiondue to the volatilization of very volatile Si. Thus, when thesemi-sintered body is sintered by pressing in the state as it is, atarget having a desired composition cannot be obtained.

[0015] Further, there is a problem that even if a semi-sintered body iscrushed and made to a powder, since hard MSi₂ particles which have beengrown once and coarsened remain without being finely crushed, a targethaving a uniform and fine structure cannot be obtained as well as anamount of contamination caused by impurities is increased by crushingand in particular an amount of oxygen is greatly increased.

[0016] On the other hand, as disclosed in Japanese Patent ApplicationLaid-Open No. Sho 62(1987)-171911, when a mixed powder is subjected to asilicide synthesization at 800-1300° C. and further deoxidized by beingheated to high temperature so as to reduce impurity oxygen, there is aproblem that since the sintering property of a resultant semi-sinteredbody is excessively improved, the semi-sintered body cannot besufficiently crushed in a subsequent crushing process and formed to asegregated structure in which MSi₂ and Si are irregularly dispersed, andin particular, when a heating temperature reaches a temperature regionexceeding 1400° C., this tendency is made more remarkable.

[0017] Although a semi-sintered body is crushed in an atmospherereplaced with Ar (argon gas) to prevent an increase of an oxygencontent, it is difficult to completely prevent the contamination byoxygen when the semi-sintered body is crushed. Further, a problem alsoarises in that when a crushed powder is taken out from a vessel such asa ball mill or the like, the powder surely adsorbs oxygen to increaseoxygen contained therein, and as a result a finely crushed powder has anincreased surface area and an amount of oxygen adsorbed by the powder isgreatly increased.

[0018] On the other hand, even if a synthesized powder was hot pressedwhile applying a preload of 60-170 kg/cm² thereto according to themethods of Japanese Patent Application Laid-Open No. Sho 63(1988)-74967and Japanese Patent Application Laid-Open No. Sho 64(1989)-39374,condensed silicon was disadvantageously produced and a target having afine and uniform structure could not be obtained.

[0019] Further, when a synthesized powder was hot pressed without beingapplied with a preload, MSi₂ grains obtained by synthesization was grownas well as a composition has an inclined distribution in a target and itwas difficult to obtain a target having a fine and uniform structure.

[0020] Japanese Patent Application Laid-Open No. Sho 62(1987)-70270discloses a refractory metal silicide target having a density ratio notless than 97%. Further, Japanese Patent Application Laid-Open No. Sho62(1987)-230676 discloses a methods of manufacturing a refractory metalsilicide target and describes that a target is molded by compactingusing a single axis under the conditions of high temperature, highvacuum and high pressing pressure.

[0021] However, the above respective prior arts describe only that atarget is made by subjecting a material powder for the target to hotpressing and no description is made as to a fine and uniform structure.Thus, these prior arts cannot achieve an object for effectivelysuppressing particles.

[0022] On the other hand, International Patent Application publishedaccording to PCT (No. WO91/18125 discloses a silicide target having400×10⁴ pieces of silicide with a grain size of 0.5-30 μm existing in across section of the mixed structure of the target of 1 mm² with themaximum grain size of Si not greater than 30 μm and further a silicidetarget with the average grain size of silicide of 2-15 μm and theaverage grain size of Si of 2-10 μm.

[0023] Since the manufacturing method described in the prior art isinsufficient to obtain a fine uniform target structure, the object tosuppress the occurrence of particles cannot be sufficiently achieved.

[0024] An object of the present invention is to provide a high densityand purity refractory metal silicide target which has a fine mixedstructure and a uniform composition as well as contains a less amount ofimpurities such as oxygen and the like, a method of manufacturing thetarget, a refractory metal silicide thin film and a semiconductordevice.

DISCLOSURE OF THE INVENTION

[0025] As a result of a zealous study why particles are generated, theinventors of this invention have obtained the following knowledge forthe first time:

[0026] (1) since free Si has a sputtering rate larger than that of MSi₂,as sputtering proceeds, MSi₂ is exposed on an erosion surface and MSi₂grains having a weak bonding force with adjacent grains are liable to beremoved from the erosion surface, and in particular very fine MSi₂grains remarkably exhibit this tendency;

[0027] (2) although the form of erosion in a free Si portion exhibits awave-shape, as the Si portion increases, the distal end of thewave-shape is made acute and further the height of the wave-shapeincreases, thus the distal end of Si is dropped off or lacked by thethermal fluctuation in sputtering so that Si is liable to becomeparticles; and

[0028] (3) when pores remain in the interface between MSi₂ and free Siof a target or in the interior of free Si, projections are formed aroundthe pores, and abnormal electric discharge occurs in the portion wherethe projections exist in sputtering, by which the projections aredropped or lacked and made to particles, and the like.

[0029] Further, the inventors have found it is very effective tosuppress the generation of the particles that:

[0030] (1) a fine mixed structure is formed such that the number of MSi₂grains (M: refractory metal) which independently exist on any arbitrarysurface or in a cross section of 0.01 mm² of the mixed structure is notgreater than 15, MSi₂ has an average grain size not greater than 10 μmand free Si existing in the gaps of MSi₂ has a maximum grain size notgreater than 20 μm;

[0031] (2) the mixed structure is arranged such that a Si/M atom ratio Xin 1 mm² of the mixed structure has a dispersion of X±0.02 and free Siis uniformly dispersed; and

[0032] (3) a density ratio is not less than 99.5% over the entiresurface of a target, and the like.

[0033] Further, the inventors have found that the growth of MSi₂ grainsproduced can be suppressed and a large dislocation (dispersion of acomposition ratio) of a composition can be prevented withoutvolatilizing almost all the Si in such a manner that when silicide issynthesized once in a silicide synthesizing process, mixed powders eachdivided to a small amount of lot are charged into a compacting mold,that is, a depth of the compacting mold to which the mixed powders arecharged is set to not deeper than 20 mm and the mixed powders are heatedin vacuum and synthesized.

[0034] Further, to reduce impurities in a target and increase itspurity, the inventors have found that:

[0035] (1) a refractory metal silicide semi-sintered body containing aless amount of oxygen not greater than 200 ppm which cannot be obtainedby prior art can be obtained in such a manner that a semi-sintered bodyobtained by synthesizing silicide is crushed once and a resultantcrushed powder is deoxidized by being heated in vacuum or in apressure-reduced hydrogen atmosphere in stead of deoxidizing thesemi-sintered body by heating it in the state as it is;

[0036] (2) when a plurality of powder charging vessels each having thesame inside diameter are prepared and crushed powders are deoxidized sothat semi-sintered bodies can be sintered in a shape as they are by ahot isostatic press method or the like, since the semi-sintered bodieshave the same shape, a plurality of semi-sintered bodies can be sinteredat the same time and there is an advantage that the productivity oftargets can be improved;

[0037] (3) when the silicide synthesis is performed in a vacuum furnaceusing a graphite heater and insulator, a semi-sintered body obtained bythe synthesization is mixed with carbon and iron and contaminated bythem. In contrast, when the silicide synthesis is performed in a vacuumfurnace using a heater and an insulator each composed of a high purityrefractory material, the contamination can be effectively prevented; and

[0038] (4) contamination caused by impurities contained in a materialcan be effectively prevented by crushing a semi-sintered body in a ballmill having a ball mill main body the inside of which is lined with ahigh purity material and crushing mediums (balls) formed of a highpurity material, and the like.

[0039] Further, as a result of a zealous study of hot pressingconditions effected by using a synthesized powder, the inventors havefound that the size of MSi₂ grains produced is different depending upona temperature for applying a pressing pressure and how the temperatureis increased and that the composition in a target has an inclineddistribution in accordance with the temperature and pressure conditions.More specifically, the inventors have found that when a synthesizedpowder is heated up to just below an eutectic temperature and thenapplied with a pressing pressure, MSi₂ grains formed by synthesizationare regrown and that free Si flows in the direction of the end of atarget and its composition has an inclined irregular distribution as theMSi₂ grains grow.

[0040] Further, the inventors have obtained the knowledge that when acertain degree of a pressing pressure is applied at a temperature stepless than 1200° C. and then heating is effected stepwise or at a lowrate up to just below an eutectic temperature and further a largerpressing pressure is applied, the growth of MSi₂ grains is effectivelyprevented, the composition in a target is made uniform and a density ofthe target is increased for the first time.

[0041] The present invention has been completed based on the aboveknowledges.

[0042] More specifically, a refractory metal silicide target accordingto the present invention is characterized by comprising a fine mixedstructure composed of MSi₂ (where M: refractory metal) grains and Sigrains, wherein the number of MSi₂ grains independently existing in across section of 0.01 mm² of the mixed structure is not greater than 15,the MSi₂ grains has an average grain size not greater than 10 μm,whereas free Si grains existing in the gaps of the MSi₂ grains have amaximum grain size not greater than 20 μm. Specifically, W, Mo, Ti, Ta,Zr, Hf, Nb, V, Co, Cr, Ni are used as the metal (M) constituting theabove metal silicide (MSi₂).

[0043] Note, the shape and the number of MSi₂ grains and Si grains inthe above mixed structure are measured as follows. That is, the maximumgrain size, average grain size and number of MSi₂ grains are measured insuch a manner that a photograph showing the structure of a targetsintered body is obtained by photographing a fracture surface of thesintered body under a scanning type electron microscope (SEM) at amagnification ratio of 1000 and thus obtained photograph is thenanalyzed with an image analyzer. A visual field to be image-analyzedmust cover 10 points.

[0044] On the other hand, the maximum grain size, average grain size andnumber of free Si grains and chain-shaped (link-formed) Si grains aremeasured in such a manner that a photograph showing the structure of atarget sintered body is obtained by photographing a polished surface ofthe sintered body under a scanning type electron microscope (SEM) at amagnification ratio of 1000, then the photograph is analyzed with animage analyzer. In that case, 5 cross sections obtained by equallydividing the polished surface in the thickness direction thereof at apitch of 10 μm were measured and when Si grains are freed from other Sigrains, they are regarded as free Si, whereas when Si grains are coupledwith other Si grains at any portion thereof, they are regarded aschain-shaped Si. A visual field must cover 20 points in each crosssection.

[0045] Since Si is more deeply eroded than MSi₂ by sputtering in theabove mixed structure, preferable is a structure arranged such that MSi₂grains are coupled each other like a chain and Si grains exist in thegaps of the MSi₂ grains to reduce particles generated in a targetbecause MSi, grains are liable to be removed or dropped from an erodedsurface in a portion where MSi₂ independently exists in Si phase.

[0046] When the size of MSi₂ grains is increased, Si is selectivelyscattered from MSi₂ and forms projections like grains. Since theseprojections are released and made to particles, the average grain sizeof MSi₂ is preferably not greater then 10 μm and more preferably notgreater than 5 μm to prevent the occurrence of the projections. On theother hand, Si is eroded to a wave-shape by sputtering, and as the sizeof Si is increased, the wave-shape is made acute and deep and Si isliable to be lacked or dropped off. Thus, the maximum grain size of Siis preferably not greater than 20 μm, more preferably not greater than15 μm, and further more preferably not greater than 10 μm.

[0047] When the average value of a Si/M atom ratio in an entire targetis assumed to be X, it is preferable that the dispersion of the Si/Matom ratio in an arbitrary cross section of 1 mm² in the mixed structureis preferably set within the range of X±0.02. That is, when MSi₂ and Siirregularly disperse even if a target has a fine structure, inparticular when free Si is locally concentrated and irregularlydistributed, since the structure in the target is greatly changed aswell as a plasma electric discharge is unstably carried out andparticles are induced, the dispersion of the Si/M atom ratio X in anarea of 1 mm² is preferably X±0.02 and more preferably X±0.01.

[0048] It is preferable to form a high density silicide target in whichthe density ratio of a target is not less than 99.5% over the entiretarget. When there remain many pores (holes) due to an insufficientdensity of a target, the pores exist in an interface between MSi₂ and Sior in the interior of Si, projections are formed around the pores insputtering, an abnormal electric discharge is caused in the portion ofthe projections and the projections are broken and released by thedischarge, which results in the occurrence of particles. Thus, the poresmust be reduced as few as possible, and for this purpose, the densityratio of target is preferably not less than 99.5%, more preferably notless than 99.7% and further more preferably not less than 99.8% over theentire target.

[0049] It is preferable that a content of oxygen as an impurity is setto not greater than 200 ppm and a content of carbon as an impurity isset to not greater than 50 ppm. When oxygen is taken into a depositedthin film by sputtering a target containing oxygen, silicon oxide isformed in the interface of the thin film and a resistance of the film isincreased by the silicon oxide. Thus, to further reduce the resistanceof the film, an oxygen content in target is preferably set to notgreater than 200 ppm and more preferably not greater than 100 ppm.Further, since carbon also increases a resistance of the film by formingsilicon carbide, a carbon content in target is preferably set to notgreater than 50 ppm and more preferably not greater than 30 ppm toreduce the resistance of the film.

[0050] The contents of iron and aluminium as impurities are set to notgreater than 1 ppm, respectively. When iron and aluminium are mixed intoa deposited thin film, a deep level is formed in the interface of thethin film and causes a leakage in connection, by which a semiconductoris poorly operated and its characteristics are deteriorated. Thus, aniron content and aluminium content in target are preferably set to notgreater than 1 ppm, respectively and more preferably not greater than0.5 ppm, respectively.

[0051] Next, a method of manufacturing a refractory metal silicidetarget according to the present invention will be described below.

[0052] In a process I (step I), a refractory metal powder having amaximum grain size not greater than 15 μm is blended with a siliconpowder having a maximum grain size not greater than 30 μm such that aSi/M atom ratio (value X in MSi_(x)) is 2-4 and these powders aresufficiently mixed each other in a dry state using a ball mill, V-typemixer or the like so that the silicon powder uniformly disperses in therefractory metal powder. The irregularly mixing of them is notpreferable because the structure and composition of a target is madeirregular and characteristics of the film formed by using the target aredeteriorated. The powders are preferably mixed in a vacuum of not higherthan 1×10⁻³ Torr or in an inert gas atmosphere such as an argon gas toprevent contamination by oxygen. In particular, when a pulverizer orpowder crushing mixer such as a ball mill or the like is used,contamination by impurities can be effectively prevented by performingmixing operation in a dry state using a ball mill having a main body theinside of which is lined with a high purity material not less than 5N(99.999%) and crushing mediums (balls) composed of a high puritymaterial so that contamination caused by impurities from a crusher mainbody can be prevented.

[0053] The same material as the refractory metal (M) constituting atarget is preferably used as the above high purity material and, forexample, W, Mo, Ti, Ta, Zr, Hf, Nb, V, Co, Cr, Ni etc. are used.

[0054] As a method of lining the pulverizer main body with the highpurity material, there can be employed a method of lining a high puritymaterial sheet, a method of integrally forming a high purity materiallayer on the inner surface of a main body by various depositing methodssuch as CVD, plasma vapor deposition, and the like.

[0055] The refractory metal powder and silicon powder used as a targetmaterial preferably contain impurities, which deterioratecharacteristics of a semiconductor device, in an amount as small aspossible and preferably have a purity not lower than 5N (99.999%).Further, since coarse powders coarsen formed MSi₂ grains and si grainsand lowers the dispersing property of Si, the refractory metal powderpreferably has a gain size not greater than 15 μm and the silicon powderpreferably has a grain size not greater than 30 μm. Further, therefractory metal powder preferably has a grain size not greater than 10μm and the silicon powder preferably has a grain size not greater than20 μm. Furthermore, the refractory metal powder preferably has a gainsize not greater than 5 μm and the silicon powder preferably has a grainsize not greater than 10 μm.

[0056] A reason why the value X of the Si/M atom ratio is limited to2≦X≦4 is as described below. That is, when the value X is less than 2,free Si reduces and further disappear in a silicide target and thestructure defined by the present invention cannot be obtained. On theother hand, when the value X exceeds 4, since free Si continuouslyexists, there is obtained a structure in which MSi₂ grains exist in a Simatrix. Consequently, the structure of the present invention that MSi₂grains are coupled each other like a chain and Si grains exist in thegaps of the MSi₂ grains is difficult to be obtained. Further, when thevalue X is less than 2, since a large tensile strength is produced in aformed silicide film, the close contact property of the film with asubstrate is deteriorated and the film is liable to be exfoliated orpeeled from the substrate. On the other hand, when the value X exceeds4, since a film resistance increases, a resultant film is improper as anelectrode wiring film. Further, when a mixed powder having the value Xnot less than 2 is synthesized to silicide, since free Si exists, thereis an advantage that a crushing property is improved in a process III tobe described below.

[0057] Si is preferably blended in an amount which is a little in excessof the amount of an intended composition by taking an loss caused by thevolatilization of a Si and SiO₂ film covering the surface of Si powdersinto account.

[0058] A process II is a process for synthesizing refractory metalsilicide as well as forming a semi-sintered body by charging the mixedpowder prepared in the process I into a compacting mold and heating thepowder in high vacuum or in an inert gas atmosphere. In the process II,since an amount of the mixed powder to be charged into the compactingmold and subjected to a synthesizing operation effected once affects thesize of MSi₂ grains to be produced and an amount of Si to bevolatilized, it is preferable to set an amount of the mixed powdercharged once to a depth not higher than 20 mm. When the depth of chargeexceeds 20 mm, formed MSi₂ grains are coarsened due to a temperatureincrease caused by a silicide reaction and the powder may be caused tooverflow from the vessel by an explosive reaction. On the other hand,when the mixed powder to be charged into the vessel has a depth nothigher than 1 mm, the number of vessels used for a single target isgreatly increased as well as an amount of production per a synthesizingtreatment is greatly reduced, and productivity is lowered. Thus, apreferable depth of charge is 1-10 mm. When Mo is used as a refractorymetal powder, however, an amount of the mixed powder to be charged intoa vessel is preferably set to a depth not higher than 10 mm and morepreferably a depth not higher than 5 mm because a particularly highcalorific value is generated by a silicide reaction.

[0059] A vessel used here is preferably composed of a high purity Mo, W,Ta, Nb material or the like to prevent the contamination of the mixedpowder caused by impurities generated from the vessel and thermaldeformation. Further, it is preferable to use the same metal material asa refractory metal (M) constituting intended refractory metal silicide.Further, the flat portion of the vessel may be set to such a shape andsize as to enable the vessel to be inserted into calcining equipmentsuch as sintering furnace.

[0060] As a heating pattern, it is preferable to effect heating stepwisefrom a temperature 200° C. lower than a silicide reaction starttemperature to suppress the growth of MSi₂ grains and minimize thechange of a composition. A temperature increasing width is preferably20-200° C. That is, when the temperature increasing width is less than20° C., a long time is needed to synthesization and productivity islowered, whereas the width exceeds 200° C. MSi₂ grains are grown and thepowder is caused to overflow from the vessel by an abrupt increase oftemperature, and a composition is changed and the interior of thefurnace is contaminated. Further, each temperature is preferably heldfor 0.1-3 hours. When the holding time is less than 0.1 hour, thetemperature of the powder in the vessel is not made uniform and atemperature difference abruptly increases, and MSi₂ grains arecoarsened. On the other hand, when the holding time exceeds 3 hours, along time is needed for synthesization and productivity is lowered.Note, the temperature increasing width is preferably set to 20-200° C.and more preferably to 50-100° C. and the holding time is morepreferably set to the range of 0.5-2 hours. In particular, when thetemperature is increased to a temperature of 100° C. or more higher thanthe silicide reaction start temperature, it is preferable to set a longholding time at the silicide reaction start temperature or within thestart temperature+50° C. and the holding time is preferably not shorterthan 1 hour. The silicide reaction start temperature can be determinedby detecting when a degree of vacuum in the furnace is lowered by thevolatilization of Si or silicon oxide (SiO or Sio₂) caused by a reactionheat.

[0061] Further, the same effect can be achieved by carrying out heatingoperation slowly in place of the stepwise heating. In this case, aheating rate is preferably controlled to 5° C./minute or less. When theheating rate is excessively large, MSi₂ grains are grown as well as thepowder is caused to overflow from the vessel, the composition is changedand the interior of a furnace is contaminated by the abrupt increase ofthe temperature.

[0062] A maximum heating temperature in synthesization is preferablyincreased up to 1100° C. so that a silicide reaction starts andsynthesization is completed. Since a reaction temperature is differentdepending upon an amount of oxygen contained in the mixed powder,however, the maximum heating temperature is preferably increased toabout 1300° C. by taking the reduction of the oxygen content intoconsideration. When the temperature is increased to higher than 1300°C., the sintering of a semi-sintered body formed by a silicide reactionproceeds and its crushing in a process III is made difficult and furtherfree Si is melted as well as MSi₂ grains are grown and coarsened by aneutectic reaction. Thus, there is obtained a structure in which MSi₂grains and Si grains irregularly disperse and as a result a silicidetarget having an intended crystal structure cannot be obtained. On theother hand, when the maximum heating temperature is not higher than1000° C., the silicide reaction does not start and synthesization ismade impossible except the case that M is Ni. Thus, a more preferabletemperature range is 1150-1250° C.

[0063] Note, when the above maximum heating temperature is excessivelyhigh in the case M is Ni, sintering is liable to proceed as comparedwith the case M is other than Ni. Thus, the temperature is preferablyincreased up to about 800° C. and more preferably in the range of700-800° C. only when Ni is used.

[0064] When a refractory metal silicide is synthesized as well as asemi-sintered body is formed in the process II, a vacuum furnaceemployed for heating is preferably, for example, a vacuum furnace usinga high purity Mo heater or a high purity W heater and an insulatorcomposed of a high purity refractory material, by which a semi-sinteredbody obtained by synthesization can be effectively protected fromcontamination caused by impurities from the heater and insulator.

[0065] In a process III, a refractory metal silicide semi-sintered bodywhich is obtained by synthesizing silicide and has an atom ratio X of2≦X≦4, is crushed or pulverized and a crushed powder is prepared. Apowder lump in which free Si segregated to an aggregation of MSi₂ formedin synthesization exists is finely crushed and uniformly dispersed bythe crushing process. When this dispersing operation is no effecteduniformly, since the dispersion of MSi₂ and free Si is lowered, thestructure and composition of a target are not uniformly arranged and afilm characteristics are deteriorated, a crushing time is preferably notshorter than 24 hours. On the other hand, although the longer thecrushing time, the more improved is a crushing efficiency, sinceproductivity is lowered and an amount of contamination is increased byoxygen, the crushing time is preferably not longer than 72 hours. Themaximum grain size of a powder obtained by the crashing is an importantfactor for obtaining a fine uniform structure defined by the presentinvention. Therefore, the maximum grain size is preferably not greaterthan 20 μm and more preferably not greater than 15 μm in order to obtainthe structure defined by the present invention that MSi₂ grains have anaverage grain size not greater than 10 m and free Si grains have amaximum grain size not greater than 20 μm.

[0066] The crushing is preferably effected in vacuum or in an inert gasatmosphere similarly to the process I to prevent the contamination byoxygen. In particular, when a crushing mixer such as a ball mill or thelike is used, contamination by impurities can be effectively preventedby carrying out mixing operation in a dry state using a ball mill havinga main body the inside of which is lined with a high purity material andcrushing mediums (balls) composed of a high purity material so thatcontamination caused by impurities from the crusher main body can beprevented.

[0067] Further, it is preferable that the following impurity removingprocess is followed by the process III to remove impurities contained inthe crushed power such as oxygen, carbon etc. That is, the impurityremoving process is a process for heating the crushed powder prepared inthe process III and preparing a high purity powder and a high puritysemi-sintered body by removing impurities such as in particular oxygenand the like therefrom. A heating temperature is preferably set to1150-1300° C. to effectively remove oxygen adsorbed to the crushedpower. More specifically, when the heating temperature is less than1150° C., it is difficult to obtain a low oxygen target containingoxygen in a amount not greater than 200 ppm by volatilizing and removingoxygen as silicon oxide (SiO or SiO₂). On the other hand, when theheating temperature exceeds 1300° C., a problem arises in that free Siis greatly volatilized and lost, and it is difficult to obtain a targethaving a predetermined composition, and further a semi-sintered body iscracked, sintering proceeds and an amount of contraction increases, andthe semi-sintered body cannot be hot pressed in the state as it is.Consequently, a more preferable temperature range is 1200-1250° C.

[0068] In particular, when the heating temperature increases, since thesemi-sintered body is liable to be cracked, it is preferable that thesemi-sintered body is processed while applying a low pressing pressurethereto. The pressure is preferably in the range not greater than 10kg/cm².

[0069] Further, the above heating temperature is preferably held for 1-8hours. When the holding time is shorter than 1 hour, oxygen isinsufficiently removed, whereas when the time exceeds 8 hours, a longtime is needed and productivity is lowered as well as a large amount ofSi is volatilized and lost, and the dislocation of the composition of asilicide target increases. Thus, the holding time is more preferably setto the range of 2-5 hours.

[0070] A degree of vacuum is preferably set to not higher than 10⁻³ Torrand further to not higher than 10⁻⁴ Torr to more effectively reduceoxygen by volatilizing silicon oxide. A further deoxidizing effect canbe obtained and a target containing a less amount of oxygen can beobtained in such a manner that after the degree of vacuum is adjusted,hydrogen is introduced into a heating furnace and the target is heatedin a pressure-reduced hydrogen atmosphere.

[0071] A vessel into which the crushed powder is charged may have ashape and size equal to those of a compacting mold to be used in asintering process such as a hot pressing or the like to be describedlater or may be formed to a size determined by taking an amount ofcontraction of a semi-sintered body caused by calcination intoconsideration. As a result, there can be obtained an advantage that adeoxidized semi-sintered body can be easily inserted into the compactingmold and a plurality of semi-sintered bodies can be simultaneouslysintered, and productivity can be greatly improved. The vessel ispreferably composed of a high purity material of Mo, W, Ta, Nb or thelike to prevent the contamination of the crushed powder by impuritiesand thermal deformation.

[0072] The crushed powder charged into the vessel is preferably smoothedby a dedicated pattern and made to flat by moving the powder forward andbackward and in rotation so that the deoxidized semi-sintered body canbe hot-pressed in the state as it is.

[0073] In a process IV, a crushed powder prepared in the process III ora semi-sintered body having been subjected to the impurity removingprocess is subjected to a main sintering and densification orcompaction. The crushed powder or semi-sintered body having beensubjected to the impurity removing process whose Si/M atomic ratio isadjusted to 2-4 and which is composed of MSi₂ and excessive Si ischarged into the compacting mold and sintered and densified whilesetting a temperature and pressure at two steps.

[0074] The compacting mold to be used here is preferably a graphitecompacting mold arranged such that, for example, a BN powder or the likehaving an exfoliation resistance at high temperature is coated on theinner surface of the mold with a spray or brush as a mold releasingagent and further a partition plate is applied onto the inside surfacethrough a double-coated adhesive tape, adhesive or the like. The moldreleasing agent is coated to prevent a compacting mold main body frombeing fused to the partition plate in hot pressing. The partition plateis provided to prevent the direct contact of the semi-sintered body withthe mold releasing agent and isolate the former from the latter. As thepartition plate, a refractory metal such as Mo, W, Ta, Nb etc. enduringhigh temperature in sintering and Ni, Ti etc. excellent in workabilityand processability is used by being formed to a thickness of 0.1-0.2 mm.When the partition plate is excessively thick, since its strength isincreased, the formability of the plate is lowered when it is appliedonto the compacting mold and workability is lowered as well as since thepartition plate is adhered onto a sintered body, a long time is neededto remove it by grinding or the like. On the other hand, when thepartition plate is too thin, since its strength is small, the plate isdifficult to handle and workability is also lowered.

[0075] The fusion of the compacting mold with the partition plate isprevented as well as the mold releasing agent is not exfoliated andremoved and the mixing of impurities contained in the mold releasingagent with a sintered body can be effectively prevented by coating themold releasing agent on the inner surface of the mold and further usingthe compacting mold on which the partition plate is applied. Inparticular, even if BN is used as the mold releasing agent, thecontamination of a target caused by inevitably contained impurities suchas aluminium, iron etc. can be effectively prevented.

[0076] Next, sintering is carried out by applying a low pressingpressure of 10-50 kg/cm² in a high vacuum not higher than 10⁻³ Torr andincreasing a temperature up to just below an eutectic temperaturestepwise or at a small temperature increasing rate.

[0077] A pressing pressure is preferably set to 10-50 kg/cm² at a firststep because the pressure affects the remaining of aggregated siliconand the grain size of MSi₂. When the pressing pressure is less than 10kg/cm, MSi₂ grains grow as well as a composition is not uniformlydistributed. On the other hand, when the pressure is not less than 50kg/cm², the ductile flow of free Si is suppressed and aggregated Siremains, and a structure in which Si is not uniformly dispersed isobtained. The pressure is more preferably 20-30 kg/cm².

[0078] When sintering is carried out by increasing a temperature up tojust below an eutectic temperature while applying a pressure, heating ispreferably effected stepwise or at a low temperature increasing rate tosuppress the growth of MSi₂ grains. A temperature increasing width ispreferably 20-200° C. When the temperature increasing width is less than20° C., a long time is needed for sintering and productivity is lowered,whereas when the width exceeds 200° C., MSi₂ grains are grown by anabrupt temperature increases as well as a composition has an inclineddistribution in a target plane due to the flow of free Si. Further, eachtemperature is preferably held for 0.1-3 hours. When the holding time isless than 0.5 hour, the temperature of a sintered body in a mold is notuniformly distributed, whereas when the time exceeds 2 hours, a longtime is needed and productivity is lowered. Thus, it is more preferablethat the temperature increasing width is set to the range of 50-100° C.and the holding time is set to the range of 0.5-2 hours.

[0079] Further, when a heating rate exceeds 20° C./minute in the heatingeffected at a low rate, MSi₂ grains are coarsened. Thus, the heatingrate is preferably set to not higher than 20° C./minute. Further, whenthe heating rate is less than 3° C./minute, since a long time is neededto sintering operation and productivity is lowered, it is preferably setto the range of 3-20° C./minute and more preferably to the range of5-10° C./minute.

[0080] A final sintering temperature T is preferably set to just belowan eutectic temperature, i.e., to the range of Ts−50≦T<Ts. When, forexample, W, Mo, Ti, Ta are used as M, the eutectic temperature Ts is1400, 1410, 1330, 1385° C., respectively. Note, the eutectic temperatureTs can be easily obtained by referring to literatures such as“Constitution of Binary Alloys” (Dr. phil. Max Hansen and Dr. KurtAnderko; McGraw-Hill Book Company, 1958) and the like. When T is nothigher than (Ts−50), pores remain and a desired high density targetcannot be obtained, whereas when T is not less than Ts, free Si ismelted and flows out from the compacting mold and a target with adislocated composition is obtained.

[0081] Since a pressing pressure at a second step affects the density ofa resultant sintered body, the pressure is preferably set to 200-500kg/cm². When the pressing pressure is less than 200 kg/cm², a sinteredbody with a density not less than 99% cannot be obtained, whereas whenthe pressure is not less than 500 kg/cm², a graphite compacting mold isliable to be broken. Thus, the pressing pressure is more preferably setto the range of 300-400 kg/cm².

[0082] The pressing pressure is preferably applied in 1-5 hours after afinal temperature is reached. When the period of time is less than 1hour, the temperature of a semi-sintered body in a mold is not madeuniform and when the pressing pressure is applied in this state, aproblem arises in that a uniform density distribution and uniformstructure cannot be obtained due to an irregular temperaturedistribution. On the other hand, when the time exceeds 5 hours, althoughthe temperature of the semi-sintered body in the mold is completely madeuniform, the holding of the semi-sintered body longer than this timelowers productivity. Thus, the holding time is preferably 2-3 hours.

[0083] Further, the pressing pressure is preferably held for 1-8 hours.When the holding time is not longer than 1 hour, many pores remain and ahigh density target cannot be obtained, whereas when it is not shorterthan 8 hours, since densification does not further proceed, themanufacturing efficiency of a target is lowered. Thus, the holding timeis more preferably 3-5 hours. The sintering for the densification ispreferably carried out in vacuum to prevent the contamination caused bythe mixture of impurities.

[0084] An intended sputtering target can be finally obtained bymachining a resultant sintered body to a predetermined shape. At thattime, it is preferable to finish the sintered body by a machining methodwhich does not produce a surface defect on the surface of the target.

[0085] A high purity silicide thin film can be formed by effectingsputtering using the target. Further, various electrodes such as a gateelectrode, source electrode, drain electrode and thin film for asemiconductor device and a thin film for wiring materials can be formedby subjecting the thin film to etching and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0086]FIGS. 1A and 1B are electron microphotographs showing the metalstructures of the polished surface and fracture surface of a targetaccording to Example 1, respectively;

[0087]FIGS. 2A and 2B are electron microphotographs showing the metalstructures of the polished surface and fracture surface of a targetaccording to Example 6, respectively;

[0088]FIGS. 3A and 3B are electron microphotographs showing the metalstructures of the polished surface and fracture surface of a targetaccording to Comparative Example 1, respectively;

[0089]FIGS. 4A and 4B are electron microphotographs showing the metalstructures of the polished surface and fracture surface of a targetaccording to Comparative Example 4, respectively;

[0090]FIG. 5 is an electron microphotograph showing the metal structureof the surface of a target semi-sintered body according to Example 11;

[0091]FIG. 6 is an electron microphotograph showing the metal structureof the surface of a target semi-sintered body according to ComparativeExample 7;

[0092]FIG. 7 is an electron microphotograph showing the metal structureof the surface of a target semi-sintered body according to ComparativeExample 8;

[0093]FIG. 8 is an electron microphotograph showing the metal structureof the surface of a target semi-sintered body according to Example 12;

[0094]FIG. 9 is an electron microphotograph showing the metal structureof the surface of a target semi-sintered body according to ComparativeExample 9; and

[0095]FIG. 10 is an electron microphotograph showing the metal structureof the surface of a target semi-sintered body according to ComparativeExample 10.

BEST MODE FOR CARRYING OUT THE INVENTION

[0096] An arrangement and advantage of the present invention will bedescribed in more detail with reference to the following examples.

EXAMPLES 1-10

[0097] A high purity M powder (M: W, Mo shown in Table 1) having amaximum grain size of 15 μm and a high purity Si powder having a maximumgrain size of 30 μm were prepared and the respective powders werecharged into a ball mill the inside of which was lined with high purityMo together with high purity Mo balls and then mixed for 48 hours withthe replacement with an Ar gas. Each of the resultant mixed powders wascharged into a high purity Mo vessel with a charging depth set to 3 mmwhen M=Mo (weight to be charged was about 250 g) and to 10 mm when M=W(weight to be charged was about 750 g) and silicide was synthesized insuch a manner that the temperature of the vessel was increased stepwisefrom 950° C. to 1300° C. with a temperature width in each step of 50° C.in a vacuum not higher than 1×10⁻⁴ Torr using a vacuum furnace having aMo heater and Mo insulator with a holding time at each step oftemperature set to 1 hour. The high purity materials used had a puritynot less than 5N (not less than 99.999%).

[0098] Next, each of semi-sintered bodies obtained by synthesizing thesilicide was charged into a ball mill the inside of which was lined withhigh purity Mo together with high purity Mo balls and then crushed andpulverized for 72 hours with the replacement of the inner atmosphere ofthe ball mill with an Ar gas. The resultant crushed powder was chargedinto a high purity Mo vessel having a diameter of 280 mm and deoxidizedby heating the vessel at 1250° C. for 4 hours in a vacuum not higherthan 10⁻⁴ Torr.

[0099] Further, the resultant semi-sintered body (about 280 mm indiameter and 40 mm thick) was set to a graphite compacting mold linedwith a Ta foil, heated to 1000° C. in a vacuum not higher than 10⁻⁴ Torrand then heated stepwise up to 1380° C. with a temperature width in eachstep of 50° C. while applying a pressing pressure of 20 kg/cm² theretowith a holding time at each step of temperature set to 1 hour. Then, thesemi-sintered body was hot pressed by a pressing pressure of 300 kg/cm²applied thereto in 2 hours after the temperature of the semi-sinteredbody had reached 1380° C., so that a sintered body having a diameter of280 mm and a thickness of 14 mm was prepared.

[0100] The resultant sintered body was subjected to grinding, polishingand electric discharging processes and finished to a target having adiameter of 258 mm and a thickness of 10 mm.

COMPARATIVE EXAMPLES 1-6

[0101] As Comparative Examples 1-6, an M powder equal to that used inExamples 1-10 was mixed with a Si powder having a maximum grain size of50 μm and silicide was synthesized in such a manner that each of theresultant mixed powders was charged into a vacuum vessel having aconventional carbon (C) heater and carbon (C) insulator and heated to1300° C. at a rate of 10° C./min in a vacuum not higher than 1×10⁻⁴ Torrwith a charging depth set to 6 mm when M=Mo and to 20 mm when M=W.

[0102] Next, the crushed powder was charged into in a graphitecompacting mold without being deoxidized and heated to 1000° C. invacuum and then heated up to 1380° C. while applying a pressing pressureof 200 kg/cm thereto, held for 2 hours and then hot pressed, in the sameway as that of Example 1, so that sintered bodies each having a diameterof 280 mm and a thickness of 14 mm were prepared.

[0103] The cross-sectional structures of Example 1-10 and ComparativeExamples 1-6 were observed under a scanning type electron microscope(SEM) and the number of MSi₂ independently existing in a cross sectionof 0.01 mm², the average grain size of MSi₂ and the maximum grain sizeof Si were measured. Table 1 shows the result of measurement. Further,FIGS. 1A, 2A, 3A and 4A show electron microphotographs of the metalstructures of the polished surfaces of target sintered bodies relatingto Examples 1 and 6 and Comparative Examples 1 and 4, respectively.FIGS. 1B, 2B, 3B and 4B show electron microphotographs of the metalstructures of the fracture surfaces of the above, target sinteredbodies, respectively. Note, the measured values are average valuesdetermined by examining a cross section at 20 positions. Further, agrain size is shown by the diameter of a minimum circle circumscribing agrain. TABLE 1 AVERAGE NUMBER OF AVERAGE MAXIMUM DISPERSION OFCOMPOSITION INDEPENDENT GRAIN SIZE GRAIN SIZE COMPOSITION SPECIMEN No.OF TARGET MSi₂ (PIECES) OF MSi₂ (μm) OF Si (μm) (Si/M ATOMIC RATIO)EXAMPLE 1 WSi_(2.8) 8 8 14 2.80 ± 0.01 EXAMPLE 2 WSi_(2.8) 5 5 15 2.80 ±0.01 EXAMPLE 3 WSi_(2.8) 8 5 11 2.80 ± 0.01 EXAMPLE 4 WSi_(2.8) 10 6 92.80 ± 0.01 EXAMPLE 5 WSi_(2.8) 14 7 13 2.80 ± 0.01 EXAMPLE 6 MoSi_(2.7)7 8 14 2.70 ± 0.01 EXAMPLE 7 MoSi_(2.7) 6 7 9 2.70 ± 0.01 EXAMPLE 8MoSi_(2.7) 8 9 10 2.70 ± 0.01 EXAMPLE 9 MoSi_(2.7) 11 6 11 2.70 ± 0.01EXAMPLE 10 MoSi_(2.7) 14 6 7 2.70 ± 0.01 COMPARATIVE WSi_(2.8) 17 18 352.75 ± 0.03 EXAMPLE 1 COMPARATIVE WSi_(2.8) 24 21 42 2.74 ± 0.03 EXAMPLE2 COMPARATIVE WSi_(2.8) 30 20 32 2.72 ± 0.04 EXAMPLE 3 COMPARATIVEMoSi_(2.7) 19 22 28 2.63 ± 0.03 EXAMPLE 4 COMPARATIVE MoSi_(2.7) 26 2438 2.61 ± 0.03 EXAMPLE 5 COMPARATIVE MoSi_(2.7) 34 25 42 2.60 ± 0.04EXAMPLE 6

[0104] As is apparent from the result shown in Table 1 and FIG. 1-FIG.4, Examples 1-10 have a fine uniform structure in which MSi₂ grains arelinked or coupled with each other like chain, the less number of MSi₂independently exist, and Si is dispersed in the gaps of the MSi₂ andfurther MSi₂ and Si have a small grain size as compared with ComparativeExamples 1-6. More specifically, it is found that in the metalstructures of the targets of the examples shown in FIGS. 1 and 2, amixed structure is formed such that fine MSi₂ grains shown by grayportions are coupled with each other like a chain and fine Si grainsshown by black portions disperse among them, whereas in the metalstructures of the targets of the comparative examples shown in FIGS. 3and 4, coarse MSi₂ grains (gray portions) and Si grains (black portions)grow as well as a ratio of fine MSi₂ grains independently existing in aSi phase is increased and thus the targets have a structure in whichparticles are liable to be generated.

[0105] Table 1 also shows the result of analysis of a Si/W atom ratio ina cross section of 1 mm² of the mixed structure of each target effectedby a surface analyzing instrument (X-ray microanalyzer: EPMA). It isfound from the result of analysis that the Examples 1-10 havecompositions nearer to an intended composition as compared with theComparative Examples 1-6 and further have uniform compositions.

[0106] Table 2 shows the result of measurement of the densities of therespective targets and the result of analysis of oxygen, carbon, ironand aluminium. TABLE 2 DISPERSION OF NUMBER OF AVERAGE COMPOSITIONDENSITY RATIO AMOUNT OF IMPURITY (ppm) PARTICLES SPECIMEN No. OF TARGET(%) O₂ C Fe Al (PIECES) EXAMPLE 1 WSi_(2.8) 99.8 ± 0.1 153 35 0.3 0.2  5EXAMPLE 2 WSi_(2.8) 99.7 ± 0.1 130 28 0.2 0.3 12 EXAMPLE 3 WSi_(2.8)99.7 ± 0.2 186 24 0.4 0.1 19 EXAMPLE 4 WSi_(2.8) 99.8 ± 0.1 120 31 0.50.3 25 EXAMPLE 5 WSi_(2.8) 99.8 ± 0.1  87 19 0.4 0.3 30 EXAMPLE 6MoSi_(2.7) 99.7 ± 0.2  95 24 0.3 0.1  6 EXAMPLE 7 MoSi_(2.7) 99.7 ± 0.1122 18 0.2 0.2 11 EXAMPLE 8 MoSi_(2.7) 99.8 ± 0.1 105 27 0.4 0.4 20EXAMPLE 9 MoSi_(2.7) 99.8 ± 0.1 145 36 0.3 0.2 24 EXAMPLE 10 MoSi_(2.7)99.7 ± 0.1 116 33 0.3 0.1 33 COMPARATIVE EXAMPLE 1 WSi_(2.8) 99.0 ± 0.3893 128  1.8 1.4 235  COMPARATIVE EXAMPLE 2 WSi_(2.8) 98.8 ± 0.4 952133  2.3 1.6 280  COMPARATIVE EXAMPLE 3 WSi_(2.8) 98.5 ± 0.3 1025  121 2.1 1.2 322  COMPARATIVE EXAMPLE 4 MoSi_(2.7) 99.1 ± 0.3 1230  158  3.42.4 256  COMPARATIVE EXAMPLE 5 MoSi_(2.7) 98.8 ± 0.4 1304  168  2.8 2.6293  COMPARATIVE EXAMPLE 6 MoSi_(2.7) 98.6 ± 0.4 1156  150  3.1 2.1 335 

[0107] As apparent from the result shown in Table 2, since the targetrelating Examples 1-10 have a density ratio not less than 99.5%, itfound that Examples 1-10 have a very small content of impurities ascompared with Comparative Examples 1-6.

[0108] The respective sputtering targets relating to Examples 1-10 andComparative Examples 1-6 were set to a magnetron sputtering apparatusand sputtered under the condition of an argon pressure of 2.3×10⁻³ Torrand a silicide film was deposited on a 6 inch Si wafer to about 3000 Åthick. The same operation was effected 10 times and an amount of mixedparticles having a particle size not less than 0.2 μm was measured andTable 2 also shows the result of the measurement. As apparent from theresult shown in Table 2, it is found that according to the targetsrelating to Examples 1-10, the number of particles mixed onto the 6 inchwafer is not greater than 33 and very small, whereas according toComparative Examples 1-6, a lot of particles which are about 10 timesthose of Examples 1-10 are generated.

EXAMPLE 11

[0109] 4658 g of a high purity (5N) W powder having a maximum grain sizeof 8 μm and 1992 g of a high purity (5N) Si powder having a maximumgrain size of 30 μm were prepared, the respective powders were chargedinto a ball mill the inside of which was lined with high purity Motogether with high purity Mo balls and then mixed for 48 hours with thereplacement of the inner atmosphere of the ball mill with an argon gas.The resultant mixed powder having a Si/W atomic ratio of 2.80 wasdivided to each charging depth of 3 mm (weight to be charged was about250 g) and charged into a high purity Mo vessel and silicide wassynthesized in such a manner that the temperature of the vessel wasincreased stepwise from 950° C. to 1300° C. with a temperature width ineach step of 50° C. in a vacuum not higher than 1×10⁻⁴ Torr using avacuum furnace having a Mo heater and Mo insulator with a holding timeat each step of temperature set to 1 hour, so that semi-sintered bodiesof Example 11 were prepared.

COMPARATIVE EXAMPLES 7-8

[0110] On the other hand, a semi-sintered body was prepared asComparative Example 7 by heating all the amount of the mixed powder fora single sheet of a target prepared in Example 11 from 950° C. to 1300°C. in vacuum at a temperature increasing rate of 10° C./minute. Inaddition, a semi-sintered body was prepared as Comparative Example 8 bydividing a mixed powder similar to that of Example 11 to each chargingdepth of 3 mm and then continuously heating the powder up to 1300° C. ata temperature increasing rate of 10° C./minute in a vacuum not higherthan 1×10⁻⁴ Torr.

[0111] The surface metal structures of respective target semi-sinteredbodies of Example 11, Comparative Examples 7 and 8 were magnified andobserved under a scanning type electron microscope (SEM) andmicrophotographs shown in FIGS. 5, 6 and 7 were obtained. Then, as theresult of examination of the maximum grain sizes of WSi₂ grains and Sigrains constituting the respective metal structures in FIG. 5-FIG. 7, itcan be confirmed that the grain sizes of the respective grains inExample 11 are smaller than those of Comparative Examples 7 and 8 and afine structure is formed and the generation of particles are morelowered in Example 11.

[0112] Table 3 shows the result of analysis of the compositions of thesemi-sintered bodies obtained by synthesization. As a result, the degreeof dislocation of the composition of Example 11 is smaller than those ofComparative Examples 7 and 8.

EXAMPLE 12

[0113] 2850 g of a high purity (5N) Mo powder having a maximum grainsize of 5 μm and 2250 g of a high purity (5N) Si powder having a maximumgrain size of 30 μm were prepared, the respective powders were chargedinto a ball mill the inside of which was lined with high purity Motogether with high purity Mo balls and then mixed for 48 hours with thereplacement of the inner atmosphere of the ball mill with an Ar gas. Theresultant mixed powder having a Si/W atomic ratio of 2.70 was divided toeach charging depth of 1.5 mm (weight to be charged was about 100 g) andcharged into a high purity Mo vessel, silicide was synthesized in such amanner that the temperature of the vessel was increased stepwise from900° C. to 1250° C. with a temperature width in each step of 50° C. in avacuum not higher than 1×10⁻⁴ Torr using a vacuum furnace having a Moheater and a Mo insulator with a holding time at each step oftemperature set to 1 hour, so that a semi-sintered body of Example 12was prepared.

COMPARATIVE EXAMPLES 9-10

[0114] On the other hand, a semi-sintered body was prepared asComparative Example 9 by heating all the amount of the mixed powder fora single sheet of the target prepared in Example 12 from 900° C. to1250° C. in the same vacuum at a temperature increasing rate of 10°C./minute. In addition, a semi-sintered body was prepared as ComparativeExample 10 by dividing a mixed powder equal to that of Example 12 toeach charging depth of 1.5 mm and then continuously heating the powderup to 1250° C. at a heating rate of 10° C./minute in a vacuum not higherthan 1×10⁻⁴ Torr.

[0115] The surface metal structures of respective target semi-sinteredbodies of Example 12, Comparative Examples 9 and 10 were magnified andobserved under a scanning type electron microscope (SEM) andmicrophotographs shown in FIGS. 8, 9 and 10 were obtained, respectively.Then, as the result of measurement of the grain size of MoSi₂ grains(gray portions) and Si grains (black portions) constituting respectivemetal structures and analysis of dispersion of the compositions of therespective semi-sintered bodies in FIGS. 8-10, the result shown in Table3 was obtained. TABLE 3 AVERAGE DISPERSION OF COMPOSITION SEMI-SINTEREDOF SEMI- BODY SPECIMEN No. SINTERED BODY COMPOSITION EXAMPLE 11WSi_(2.79) 2.79 ± 0.01 EXAMPLE 12 MoSi_(2.68) 2.68 ± 0.01 COMPARATIVEWSi_(2.65) 2.65 ± 0.03 EXAMPLE 7 COMPARATIVE WSi_(2.69) 2.69 ± 0.04EXAMPLE 8 COMPARATIVE MoSi_(2.45) 2.45 ± 0.03 EXAMPLE 9 COMPARATIVEMoSi_(2.56) 2.56 ± 0.04 EXAMPLE 10

[0116] As is apparent from the result shown in Table 3 and FIGS. 8-10,the grain size of MoSi₂ grains in Example 12 is smaller than that ofComparative Examples 9 and 10 and Example 12 can obtain a fine uniformmetal structure with a small grain size.

[0117] Further, as the result of analysis of the compositions of thesemi-sintered bodies obtained by the synthesization, it is found thatExample 12 can provide a target whose composition is less dislocatedthan the targets of Comparative Examples 9 and 12 and which is morehomogeneous than the targets thereof.

[0118] Next, a difference of deoxidizing effects will be described.

EXAMPLE 13

[0119] The semi-sintered body obtained in Example 11 was charged into aball mill the inside of which was lined with a high purity Mo materialtogether with high purity Mo balls and crushed for 48 hours with thereplacement of the inner atmosphere of the ball mill with an Ar gas. Theresultant crushed powder was charged into a high purity Mo vessel havinga diameter of 280 mm and the vessel was heated at 1250° C. for 4 hoursin a vacuum not higher than 1×10⁻⁴ Torr.

EXAMPLE 14

[0120] On the other hand, a mixed powder equal to that of Example 13 washeated at 1100° C. for 4 hours in a vacuum not higher than 1×10⁻⁴ Torras Example 14.

[0121] Table 4 shows the result of analysis of oxygen in the respectivesemi-sintered bodies of Example 13 and Example 14.

[0122] As is apparent from the result shown in Table 4, it is confirmedthat an oxygen content of Example 13 is reduced to about {fraction(1/3)} that of Example 14.

EXAMPLE 15

[0123] The semi-sintered body obtained in Example 12 was charged into aball mill the inside of which was lined with a high purity Mo materialtogether with high purity Mo balls and crushed for 48 hours with thereplacement of the inner atmosphere of the ball mill with an Ar gas. Theresultant crushed powder was charged into a high purity Mo vessel havinga diameter of 280 mm and the vessel was heated at 1250° C. for 4 hoursin a vacuum not higher than lx 10⁻⁴ Torr.

EXAMPLE 16

[0124] On the other hand, a mixed powder equal to that of Example 15 washeated at 1100° C. for 4 hours in a vacuum not higher than 1×10⁻⁴ Torras Example 16.

[0125] Table 4 shows the result of analysis of oxygen content in therespective semi-sintered bodies of Example 15 and Example 16.

EXAMPLE 17

[0126] The semi-sintered body obtained in Example 11 was charged into aball mill the inside of which was lined with a Mo high purity materialtogether with high purity Mo balls and crushed for 48 hours with thereplacement of the inner atmosphere of the ball mill with an Ar gas. Theresultant crushed powder was charged into a high purity Mo vessel havinga diameter of 280 mm, the vessel was evacuated to 1×10⁻⁴ Torr andhydrogen was introduced into the vessel and then the vessel was heatedat 1250° C. for 4 hours in an atmosphere reduced to 0.1 Torr. Table 4shows the result of analysis of the oxygen content of the resultantspecimens (semi-sintered bodies). TABLE 4 AMOUNT OF OXYGEN SPECIMEN No.(ppm) EXAMPLE 13 110 EXAMPLE 14 380 EXAMPLE 15 140 EXAMPLE 16 140EXAMPLE 17 85

[0127] As is apparent from the result shown in Table 4, according toExample 15, the oxygen content of the semi-sintered body is reduced toabout {fraction (1/3)} that of Example 16.

[0128] Further, as shown in Example 17, a higher deoxidizing effect canbe obtained when impurities are removed in a reduced pressure atmospherewith hydrogen introduced thereinto rather than when they are removed ina simple vacuum atmosphere.

[0129] As described above, the semi-sintered bodies of the refractorymetal silicide obtained by the manufacturing method of the examples caneasily provide a target with a low oxygen content because thesemi-sintered bodies contain a very small amount of oxygen. As a result,the employment of the target can reduce a film resistance and improvethe reliability of semiconductor devices.

EXAMPLES 18-23

[0130] A high purity W powder or high purity Mo powder each having amaximum grain size of 15 μm was mixed with a high purity Si powderhaving a maximum grain size of 30 μm, and silicide was synthesized byheating the resultant mixed powder in vacuum. Further, manysemi-sintered bodies of 280 mm in diameter and 40 mm thick having anaverage composition of WSi_(2.8) or MoSi_(2.7) were prepared in such amanner that a semi-sintered body obtained by synthesizing the silicidewas crushed in a ball mill and the resultant crushed powder wasdeoxidized by being heated in vacuum.

[0131] Next, silicide targets relating to Examples 18-23, respectivelywere made by subjecting the resultant semi-sintered bodies obtained tohot pressing under a pressing condition and heating condition eachcomposed of two steps shown in Table 5. Note, the heating condition wassuch that the semi-sintered bodies were continuously heated up to 1000°C. at a temperature increasing rate of 5-20° C./minute and then heatedstepwise from 1000° C. to 1380° C. with a temperature width in each stepof 50-150° C.

COMPARATIVE EXAMPLES 11-15

[0132] On the other hand, the semi-sintered bodies used in Examples19-23 were hot pressed under a pressing condition and heating conditionseach composed of two steps, and silicide targets relating to ComparativeExamples 11-15 were made.

[0133] The mixed structures of the resultant silicide targets relatingto Examples 18-23 and Comparative Examples 11-15 were observed under ascanning type electron microscope and the average grain size of WSi₂grains and MoSi₂ grains and the maximum grain size of Si grainsconstituting the mixed structures were measured and the compositions ofthe respective silicide targets were analyzed at the center portions andend portions thereof. Table 5 shows the result of the measurement andanalysis. TABLE 5 AVERAGE COMPOSITION PRESSURIZING HEATING CONDITIONSGRAIN MAXIMUM OF TARGET AVERAGE CONDITIONS HOLDING SIZE OF GRAIN (Si/MATOMIC RATIO) SPECIMEN COMPOSITION 1st STEP 2nd STEP TEMPERATURE PERIODMSi₂ SIZE OF Si END CENTER No. OF TARGET (kg/cm²) (kg/cm²) WIDTH (° C.)OF TIME (hr) (μm) (μm) PORTION PORTION EXAMPLE 18 WSi_(2.8) 20 300  50 18  8 2.78 2.79 EXAMPLE 19 WSi_(2.8) 30 300 100 2 7 10 2.79 2.79 EXAMPLE20 WSi_(2.8) 40 300 150 3 5 14 2.79 2.79 EXAMPLE 21 MoSi_(2.7) 10 300 50 1 7  7 2.68 2.69 EXAMPLE 22 MoSi_(2.7) 20 300 100 2 6 10 2.69 2.69EXAMPLE 23 MoSi_(2.7) 30 300 150 3 5 14 2.69 2.69 COMPAR- WSi_(2.8) 250 300 100 2 6 25 2.79 2.79 ATIVE EXAMPLE 11 COMPAR- WSi_(2.8) 30 300 400 112  12 2.77 2.80 ATIVE EXAMPLE 12 COMPAR- MoSi_(2.7) 150  300  50 1 6 222.68 2.69 ATIVE EXAMPLE 13 COMPAR- MoSi_(2.7) 200  300 100 2 8 27 2.682.69 ATIVE EXAMPLE 14 COMPAR- MoSi_(2.7)  0 300 400 1 15  15 2.65 2.69ATIVE EXAMPLE 15

[0134] In the targets relating to Examples 18-23, since Si plasticallyflows, disperses and moves to the gaps of the semi-sintered bodies andfills the gaps under the condition of a low pressing pressure, a lessamount of Si is segregated and uniformly dispersed. Thus, as apparentfrom the result shown in Table 5, the WSi₂ grains, MoSi₂ grains and Sigrains of the targets of the respective examples have grain sizessmaller than those of the comparative examples, so that fine andminiaturized mixed structures are obtained. Further, it is found thatthe composition (Si/M atomic ratio) of each of the targets of theexamples is less dispersed at the center and end portion thereof andexhibits a composition more uniformly distributed than that of thecomparative examples.

[0135] On the other hand, it is found that when a high pressure isapplied from the initial stage of the start of sintering as in thetargets of Comparative Examples 11, 13, 14, since a Si component isrestricted and plastic flowing is difficult to occur, Si grains arecoarsened and a fine mixed structure cannot be obtained.

[0136] Further, it is also found that when targets are abruptly heatedunder a low pressing pressure as in the targets of Comparative Examples12 and 15, MSi₂ grains grow and a fine structure cannot be obtainedlikewise.

EXAMPLES 24-34

[0137] A high purity M (M: W, Mo, Ti, Zr, Hf, Nb, Ta, V, Co, Cr, Nishown in Table 6) powder having a maximum grain size of 15 μm and a highpurity Si powder having a maximum grain size of 30 μm were prepared andthe respective powders were charged into a ball mill the inside of whichwas lined with high purity Mo together with high purity Mo balls andmixed for 48 hours with the replacement of the inner atmosphere of theball mill with an Ar gas. The resultant respective mixed powders werecharged into a high purity Mo vessel. The depth and weight of the mixedpowders to be charged were set to 5 mm and about 2000 g, respectively.The vessel was then heated stepwise in the temperature range from 800°C. to 1300° C. (different depending upon a material) in a vacuum nothigher than 1×10⁻⁴ Torr with a temperature width in each step of 50° C.with a holding time at each step temperature set to 1 hour, so thatsilicide was synthesized. High purity materials not less than 5N wereused as the respective high purity materials.

[0138] Next, semi-sintered bodies obtained by synthesizing the suicidewere charged into a ball mill the inside of which was lined with highpurity Mo together with high purity Mo balls and then mixed for 48 hourswith the replacement of the inner atmosphere of the ball mill with an Argas. The resultant crushed powders were charged into a high purity Movessel having a diameter of 280 mm and the vessel was heated at 1250° C.for 4 hours in a vacuum not higher than 1×10⁻⁴ Torr to subject thepowders to a deoxidizing treatment.

[0139] Further, resultant semi-sintered bodies (about 280 mm indiameter×40 mm thick) were set to a graphite compacting mold the insideof which was lined with a Ta foil and heated to 1000° C. in a vacuum nothigher than 1×10⁻⁴ Torr. Then, the temperature of the semi-sinteredbodies was increased stepwise up to a temperature 30° C. lower than theeutectic temperature of each material (final temperature) with atemperature width in each step of 50° C. with a holding time of eachtemperature set to 1 hour while applying a low pressing pressure of 20kg/cm to the semi-sintered bodies. Then, the semi-sintered bodies werehot pressed with a high pressing pressure of 350 kg/cm in 2 hours afterthe final temperature was reached, so that sintered bodies each having adiameter of 280 mm and a thickness of 14 mm were made.

[0140] The resultant sintered bodies were subjected to grinding,polishing and electric discharging processes and finished to targetseach having a diameter of 258 mm and a thickness of 10 mm.

COMPARATIVE EXAMPLES 16-26

[0141] As Comparative Examples 16-26, an M powder similar to that ofExamples 24-34 was mixed with a Si powder having a maximum grain size of50 μm and the resultant respective powders were charged into a vacuumfurnace having a conventional carbon (C) heater and carbon (C) insulatorwith a charging depth set to 20 mm and heated to the temperature rangefrom 800 to 1300° C. (different depending upon a material) at a rate of10° C./minute in a vacuum not higher than 1×10⁻⁴ Torr and semi-sinteredbodies were obtained by synthesizing silicide.

[0142] Next, the semi-sintered bodies obtained by synthesizing thesilicide were set to a graphite compacting mold without being deoxidizedand heated to 1000° C. in vacuum. Then, the temperature of thesemi-sintered bodies was increased up to a temperature 30° C. lower thanthe eutectic temperature of each material (final temperature) whileapplying a pressing pressure of 200 kg/cm² to the semi-sintered bodies.Then, the semi-sintered bodies were held for 2 hours to be hot pressed,so that sintered bodies each having a diameter of 280 mm and a thicknessof 14 mm were made and further finished to targets having the samedimension as that of the above examples.

[0143] The cross-sectional structures of the respective targets relatingto Example 24-34 and Comparative Examples 16-26 were observed under ascanning type electron microscope (SEM) and the number of MSi₂independently existing in a cross section of 0.01 mm², the average grainsize of MSi₂ and the maximum grain size of Si were measured. Table 6shows the result of the measurement. Note, the measured values areaverage values determined by examining a cross section at 20 positions.Further, a grain size is shown by the diameter of a minimum circlecircumscribing a grain. TABLE 6 (To be continued) AVERAGE NUMBER OFAVERAGE MAXIMUM DISPERSION OF COMPOSITION INDEPENDENT GRAIN SIZE GRAINSIZE COMPOSITION SPECIMEN No. OF TARGET MSi₂ (PIECES) OF MSi₂ (μm) OF Si(μm) (Si/M ATOMIC RATIO) EXAMPLE 24 WSi_(2.8) 9 7 15 2.80 ± 0.01 EXAMPLE25 MoSi_(2.7) 10 9 13 2.70 ± 0.01 EXAMPLE 26 TiSi_(2.7) 6 7 15 2.70 ±0.01 EXAMPLE 27 ZrSi_(2.6) 12 9 12 2.60 ± 0.01 EXAMPLE 28 HfSi_(2.5) 107 10 2.50 ± 0.01 EXAMPLE 29 NbSi_(2.7) 8 5 11 2.70 ± 0.01 EXAMPLE 30TaSi_(2.6) 6 8 9 2.60 ± 0.01 EXAMVLE 31 VSi_(2.5) 9 7 13 2.50 ± 0.01EXAMPLE 32 CoSi_(2.6) 11 9 12 2.60 ± 0.01 EXAMPLE 33 CrSi_(2.7) 7 7 102.70 ± 0.01 EXAMPLE 34 NiSi_(2.7) 12 9 13 2.70 ± 0.01

[0144] As apparent from the result shown in Table 6, Examples 24-34 havea uniform and fine structure in which the less number of MSi₂independently exist and Si disperses in the gaps of the MSi₂, andfurther MSi₂ and Si have a small grain size as compared with ComparativeExamples 16-26. Further, in each of the targets of the respectiveexamples, a mixed structure is formed such that fine MSi₂ grains shownby white portions are coupled with each other like a chain and fine Sigrains shown by black portions disperse among them similarly to themetal structures of the targets of Examples 1 and 6 shown in FIGS. 1 and2. On the other hand, it is found that in the targets relating toComparative Examples 16-26, coarse MSi₂ grains (gray portions) and Sigrains (black portions) grow as well as a ratio of fine MSi₂ grainsindependently existing in a Si phase is increased and thus the targetshave a structure in which particles are liable to be generated similarlyto the metal structures of the targets relating to Comparative Examples1 and 4 shown in FIGS. 3 and 4.

[0145] Table 6 also shows the result of analysis of a Si/W atomic ratioin a cross section of 1 mm² of the mixed structure of each targetobtained by a surface analyzing instrument (X-ray microanalyzer: EPMA).It is found from the result of analysis that the examples havecompositions nearer to an intended composition as compared with thecomparative examples and further have uniform compositions.

[0146] Table 7 shows the result of measurement of the densities of therespective targets and the result of analysis of oxygen, carbon, ironand aluminium. TABLE 7 AVERAGE NUMBER OF COMPOSITION DISPERSION OFAMOUNT OF IMPURITY (ppm) PARTICLES SPECIMEN No. OF TARGET DENSITY RATIOO₂ C Fe Al (PIECES) EXAMPLE 24 WSi_(2.8) 99.8 ± 0.1 135  30 0.4 0.1  8EXAMPLE 25 MoSi_(2.7) 99.8 ± 0.1 141  25 0.5 0.3  9 EXAMPLE 26TiSi_(2.7) 99.7 ± 0.1 185  33 0.6 0.2  15 EXAMPLE 27 ZrSi_(2.6) 99.8 ±0.1 122  30 0.5 0.3  16 EXAMPLE 28 HfSi_(2.5) 99.8 ± 0.1 179  34 0.7 0.3 13 EXAMPLE 29 NbSi_(2.7) 99.8 ± 0.1 165  25 0.5 0.2  17 EXAMPLE 30TaSi_(2.6) 99.7 ± 0.2 143  37 0.6 0.3  9 EXAMPLE 31 VSi_(2.5) 99.7 ± 0.1178  35 0.7 0.3  17 EXAMPLE 32 CoSi_(2.6) 99.8 ± 0.1 188  38 0.6 0.2  18EXAMPLE 33 CrSi_(2.7) 99.7 ± 0.1 155  31 0.8 0.4  14 EXAMPLE 34NiSi_(2.7) 99.7 ± 0.2 187  40 0.8 0.3  20 COMPARATIVE EXAMPLE 16WSi_(2.8) 99.1 ± 0.3 954 117 2.1 2.2 257 COMPARATIVE EXAMPLE 17MoSi_(2.7) 99.0 ± 0.3 1180  123 3.1 2.3 277 COMPARATIVE EXAMPLE 18TiSi_(2.7) 98.5 ± 0.4 3475  188 4.5 3.3 327 COMPARATIVE EXAMPLE 19ZrSi_(2.6) 98.6 ± 0.3 1946  170 3.8 2.2 244 COMPARATIVE EXAMPLE 20HfSi_(2.5) 98.8 ± 0.3 1737  152 3.2 3.1 217 COMPARATIVE EXAMPLE 21NbSi_(2.7) 98.7 ± 0.4 2254  162 4.0 2.9 289 COMPARATIVE EXAMPLE 22TaSi_(2.6) 98.5 ± 0.4 2790  189 4.2 3.1 336 COMPARATIVE EXAMPLE 23VSi_(2.5) 98.6 ± 0.3 2774  175 3.9 2.7 297 COMPARATIVE EXAMPLE 24CoSi_(2.6) 99.0 ± 0.3 1995  147 3.5 2.5 207 COMPARATIVE EXAMPLE 25CrSi_(2.7) 98.7 ± 0.3 2065  155 3.7 2.6 268 COMPARATIVE EXAMPLE 26NiSi_(2.7) 98.4 ± 0.4 3358  189 4.5 3.9 357

[0147] As is apparent from the result shown in Table 7, it was foundthat the targets relating to Examples 24-34 have a density ratio notless than 99.5% and a very small content of impurities as compared withthe targets relating to Comparative Examples 16-26.

[0148] The respective targets relating to Examples 24-34 and ComparativeExamples 16-26 were set to a magnetron sputtering apparatus andsputtered under the condition of an argon pressure of 2.3×10⁻³ Torr anda silicide film was deposited on a 6 inch Si wafer to about 3000Å thick.The same operation was repeated 10 times and an amount of mixedparticles having a particle size not less than 0.2 μm was measured.Table 7 also shows the result of the measurement. As also apparent fromthe result shown in Table 7, according to the targets relating toExamples 24-34, the number of particles mixed on the 6 inch wafer is notgreater than 20 and very small, whereas according to ComparativeExamples 16-26, it is found that a lot of particles which are about 10times those of Examples 24-34 are generated.

[0149] Industrial Applicability:

[0150] As described above, the refractory metal silicide targetsaccording to the present invention have a high purity, high density finemixed structure composed of refractory metal silicide grains and Sigrains in which Si grains uniformly disperse and, the compositions inthe targets are uniformly arranged. Consequently, the employment of thetargets reduces particles produced in sputtering, the change of a filmresistance on a wafer surface and the impurities and the like in thefilm of the wafer face and can improve yield and reliability whensemiconductors are manufactured.

1. A refractory metal silicide target, comprising a fine mixed structurecomposed of MSi₂ (where M: at least one kind of a refractory metalselected from W, Mo, Ti, Ta, Zr, Hf, Nb, V, Co, Cr, Ni) grains and Sigrains, wherein the number of MSi₂ grains independently existing in across section of 0.01 mm² of the mixed structure is not greater than 15,the MSi₂ grains have an average grain size not greater than 10 μm,whereas free Si grains existing in gaps of the MSi₂ grains have amaximum grain size not greater than 20 μm.
 2. A refractory metalsilicide target according to claim 1 , wherein when the average value ofa Si/M atomic ratio in the entire sputtering is assumed to be X, thedispersion of the Si/M atomic ratio in an arbitrary cross section of 1mm² in the mixed structure is in a range of X±0.02.
 3. A refractorymetal silicide target according to claim 1 , wherein a density ratio isnot less than 99.5% over the entire target.
 4. A refractory metalsilicide target according to claim 1 , wherein an oxygen content is notgreater than 200 ppm and a carbon content is not greater than 50 ppm. 5.A refractory metal silicide target according to claim 1 , wherein aniron content and an aluminium content are not greater than 1 ppm,respectively.
 6. A method of manufacturing a refractory metal silicidetarget comprising a fine mixed structure composed of MSi₂ (where M: atleast one kind of a refractory metal selected from W, Mo, Ti, Ta, Zr,Hf, Nb, V, Co, Cr, Ni) grains and Si grains, wherein the number of MSi₂grains independently existing in a cross section of 0.01 mm² of themixed structure is not greater than 15, the MSi₂ grains have an averagegrain size not greater than 10 μm, whereas free Si grains existing ingaps of the MSi₂ grains have a maximum grain size not greater than 20μm, the method comprising the processes of: I. preparing a mixed powderby mixing a high purity refractory metal powder having a maximum grainsize not greater than 15 μm with a high purity silicon powder having amaximum grain size not greater than 30 μm such that a Si/M atomic ratiois 2-4; II. synthesizing a refractory metal silicide as well as forminga semi-sintered body by charging the mixed powder into a vessel andheating the powder up to 1300° C. in vacuum; III. preparing a crushedpowder by crushing the semi-sintered body in vacuum or in an inert gasatmosphere; and IV. charging the crushed powder into a compacting mold,increasing the temperature of the crushed powder to just below aneutectic temperature in vacuum or in an inert gas atmosphere at atemperature less than 1200° C. while applying a low pressing pressure of10-50 kg/cm² to the crushed powder, and then densifying the powder undera high pressing pressure of 200-500 kg/cm².
 7. A method of manufacturinga refractory metal silicide target according to claim 6 , wherein animpurity removing process is provided between process III and process IVto prepare a high purity powder by reducing impurities such as oxygen,carbon etc. in such a manner that the crushed powder prepared in processIII is charged into a vessel and heated to 1100-1300° C. in vacuum.
 8. Amethod of manufacturing a refractory metal silicide target according toclaim 6 , wherein an impurity removing process is provided betweenprocess III and process IV to prepare a high purity powder by reducingimpurities such as oxygen, carbon etc. in such a manner that the crushedpowder prepared in process III is charged into a vessel and heated to1100-1300° C. in an pressure-reduced hydrogen atmosphere.
 9. A method ofmanufacturing a refractory metal silicide target according to claim 6 ,wherein the mixed powder to be charged into the vessel for a heattreatment effected once in process II is set to a depth not greater than20 mm.
 10. A method of manufacturing a refractory metal silicide targetaccording to claim 7 , wherein the inside diameter of the vessel intowhich the crushed powder is charged in the impurity removing process isset equal to the inside diameter of the compacting mold into which thecrushed powder is charged in process IV.
 11. A refractory metal silicidethin film, formed by using a refractory metal silicide target comprisinga mixed structure composed of MSi₂ (where M: at least one kind of arefractory metal selected from W, Mo, Ti, Ta, Zr, Hf, Nb, V, Co, Cr, Ni)grains and Si grains, wherein the number of MSi₂ grains independentlyexisting in a cross section of 0.01 mm² of the mixed structure is notgreater than 15, the MSi₂ grains have an average grain size not greaterthan 10 μm, whereas free Si grains existing in gaps of the MSi₂ grainshave a maximum grain size not greater than 20 μm.
 12. A refractory metalsilicide thin film according to claim 11 , wherein the refractory metalsilicide thin film is a thin film constituting at least one kind of agate electrode, source electrode, drain electrode and wire of asemiconductor device.
 13. A semiconductor device, including at least onekind of a gate electrode, source electrode, drain electrode and wirecomprising a refractory metal silicide thin film formed by using arefractory metal silicide target comprising a fine mixed structurecomposed of MSi₂ (where M: at least one kind of a refractory metalselected from W, Mo, Ti, Ta, Zr, Hf, Nb, V, Co, Cr, Ni) grains and Sigrains, wherein the number of MSi₂ grains independently existing in across section of 0.01 mm² of the mixed structure is not greater than 15,the MSi₂ grains have an average grain size not greater than 10 μm,whereas free Si grains existing in gaps of the MSi₂ grains have amaximum grain size not greater than 20 μm.